Spear guns are commonly used to hunt fish or other underwater animals. Spear guns typically include a spear, a barrel, and a firing mechanism for firing the spear from the barrel. Several different types of spear guns exist, including gas-powered spear guns and band-powered spear guns. In conventional band-powered spear guns, the spear is supported on the barrel and is fired by one or more elastic bands stretched between a slot in the front end of the barrel and the rear end of the spear. The power of the band-powered spear gun may be adjusted by adding or removing one or more elastic bands. In conventional gas-powered spear guns, the spear is launched from the barrel of the spear gun with a high velocity that causes cavitation of the water immediately behind the spear (i.e., in the wake of the traveling spear). The cavitation of the water creates a relatively low pressure area behind the spear that impedes or retards the travel of the spear through the water and thereby limits the power, range, and efficacy of the spear.
Some conventional spears address the problem of cavitation by pressurizing a hollow spear with a high-pressure charge (e.g., 1000 psig) prior to firing the spear. The pressurized spear is typically retained in the barrel of the spear gun with a trigger sear that must be disengaged to fire the spear. However, pre-pressurizing the spear with the firing charge prevents the user from unloading the spear from the barrel of the spear gun without having to fire the spear or otherwise wasting the high-pressure charge. This is both wasteful and inconvenient if a user wishes unload the spear but has not found a suitable target in the water. Additionally, the high-pressure charge may leak over time and therefore may supply an insufficient charge to adequately launch the spear once the user is ready to fire the spear.